I know this is off topic, but .....
Bit Torrent (BT) relies on being able to work with a large file being broken up into loads of much smaller ones.
When you download using BT, you are downloading parts of those small files with the eventual goal of having downloaded all of them. As you work your way towards 100% download, your BT application allows other users to access the data that you have already downloaded and they can then upload that.
The BT application I use allows me to see each of those pieces of the main file and I can see what percentage of those pieces has already been downloaded. It also allows me to throttle the bandwidth so preventing the uploaders hogging all my outgoing bandwidth.
The average split so far of me downloading and them uploading is about 4 to1 in favour of the uploaders
I can also see the IP address of the "person/persons" downloading from me and from whom I am downloading. That means that Big Brother can also see that information if they want to.
I haven't yet managed to figure out how to block outgoing traffic to people who are taking from me but are not also giving anything back!
Essentially, it's a rather well designed way of statistically spreading the load over many PCs allowing the best possible chance of getting all the bits you need to reconstruct the original file(s) because you don't have to download the files in a strict serial sequence ... if you see what I mean.
Do search for Bit Torrent and have a read through some of the FAQs on the subject.
Hope that helps.
ST